I do have my home automation build on CAN nodes with teensy-3.2. I went into the rabbit hole of the Board design with some sucess (https://wiebel.org/CANNode/ for those who are interested)
I used to have a RasPi with an SPI CAN controller as a Gateway, I always wanted to go for a Beaglebone Black because of it’s native DCAN. So I ordered the RS485/CAN Cape from waveshare.
It looks like it’s the only Cape available for a reasonable price. After ordering I checked the Schematics and got shocked about how awful the design was.
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shared TX/RX for CAN and RS485 so you can’t use both
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DCAN0 is not accessible
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forced 120Ohm termination, no jumper to turn it of
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Rs is pulled down by 10k
I got over or around the first points (desoldered the 120Ohm). But the last one bit me, althoug I haven’t noticed it at first glance.
All CAN bus activities are suppressed as long as the Interface is not properly enabled in the beaglebone. I figured to better enable it right at boot time, turns out that is not noing to happen in early boot.
After some reasoning I noticed that the flexcan library on the teensy very well supports the Rs pin which I have connected to a gpio, So the Tranceiver gets enabled when all is set.
As it seems like I have to roll my own cape I’d rather try to make it properly.
So here are my questions:
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Is there any predefined way for the dcan driver to enable the tranceiver or do I need to fix it manually?
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What pin might be prefereable for such a need or is least often used by other capes?
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What is the initial state of the pins at boot time
The Datasheet of the AM3358/9 have no mention of additional pins used for CAN.